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BULLLTINNo.  18 
DLPARTMLNT  OF  CLRAMIC5 

A.  V.  BLLININGLR.  Director 

A   THERMAL   5TUDY    OF     BORIC     ACID-51LICA 

MIXTURES 

BY 
A.  V.  BLLININGLR  AND  PAUL  TLLTOR 


THE  REPLACEMENT  OF  TIN  OXIDE  BY  ANTIMONY 
OXIDE  IN  ENAMEL5  FOR  CA5T  IRON 

BY 

R.  L.  BROWN 


191  1-1912 


PUBLISHED  rORTNIGHTLY  BY  (HL  UNIVERSITY 


[Reprinted  from  Transactions  American  Ceramic  Society,     Vol.  XIV, 
BY  Permission.] 

A  THERMAL  STUDY   OF   BORIC   ACID-SILICA  MIXTURES. 

By  A.  V.   Bleixixger  and  Pali.  Teetok,  Urbana,  111. 

The  subject  of  possible  chemical  combinations  of  silica 
and  boric  acid  has  received  some  attention  in  our  Transactions,'-^ 
and  the  question  raised  is  interesting  inasmuch  as  such  mixtures 
possess  most  decidedly  the  character  of  glasses  or  solid  solutions. 
Thermal  analysis  thus  does  not  promise  a  fruitful  field  of  in- 
vestigation. However,  of  the  two  methods  com])rising  thermal 
analysis,  the  determinations  of  the  softening  temperatures  is  of 
some  interest  in  itself,  since  it  gives  us  the  general  character 
of  the  fusion  curve  of  the  two  components  involved. 

A  thermal  lag  is  not  to  be  expected  either  in  the  heating 
or  cooling  curves.  In  the  present  work,  a  search  was  made,  how- 
ever, for  such  a  point  based  on  the  statement  of  Binns,  Trans. 

A.  C.  S.,  X,  p.  158,  in  which  he  records  a  temperature  increase 
upon  the  fusion  of  a  mixture  of  boric  acid  and  silica,  due  to 
some  exothermal  change.  The  present  research  deals,  (a)  with  the 
determination  of  the  softening  points  of  Si02-B203  mixtures  be- 
tween the  limits  Bp.,-B.O.j.3Si02,  (b)  with  the  determination 
of  heating  and  cooling  curves  and  (c)  with  an  investigatio^i  of  the 
solubility  of  the  fused  glasses  in  water.  The  reagents  used  were 
chemically  pure  hydrous  boric  acid  and  silica,  the  latter  being  a 

B.  &  A.  preparation  which  unfortunately  contained  several  per 
cent,  of  sodium  chloride  and  water.  In  the  latter  part  of  the 
series,  fusions  were  made  also  with  fiint  which  had  been  passed 
through  a  200  mesh  sieve.  The  calculation  of  the  mixtures 
was  based  upon  the  analyzed  silica  content,  practically  97  per 
cent.  The  boric  acid  was  fused,  cooled  rapidly  and  kept  in  a 
desiccator.  It  was  crushed  in  a  porcelain  and  pulverized  in  an 
agate  mortar.  Similarly,  the  silica  was  ignited  and  kept  in  a 
desiccator.  The  mixtures  were  ground  together  in  the  agate 
mortar  and  fused  over  the  blast  lamp  in  a  10  cc.  platinum  crucible 
kept  covered  during  the  heating.  After  some  time,  the  yellow 
color  of  the  mass  disappeared,  which  seemed  to  be  a  measure 
of  the  completeness  of  the  fusion.     The  cooled  mass  had  an  opaque 


>  Binns,  Trans.  A.  C.  S.,  Vol.  X,  p.   158. 
2  Singer,  Trans.  A.  C  S.,  Vol.  XI.  p.  676. 


4  A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 

but  glassy  appearance.  The  fused  mixture  was  easily  removed 
from  the  crucible  by  inserting  a  platinum  rod  and  quickly  cooling 
in  cold  water.  Then  the  fusion  was  pulverized  and  screened 
through  So  and  150  mesh  screens.  The  portion  passing  the  80 
but  remaining  on  the  150  mesh  screen  was  used  for  the  solubility 
samples.  This  was  done  in  order  that  no  great  variations  in 
the  surface  factor  might  affect  the  solubility  of  the  several  mix- 
tures. 

SOFTENING  POINT  DETERMINATION. 

For  this  purpose,  the  fused  mixtures  of  SiO^  and  B2O3, 
ground  to  a  fine  powder,  were  made  up  with  a  little  water  into 
small  cones,  and  placed  in  an  electric  resistance  furnace.  The 
specimens  were  kept  in  position  by  means  of  platinum  foil.  Since 
in  glasses  practically  no  other  criterion  is  available  than  the 
deformation  point,  the  temperature  at  which  the  cones  bent  was 
taken  to  represent  the  softening  point.  Care  was  taken  to  raise 
the  heat  at  a  regular  rate  by  rheostat  regulation,  and  the  tempera- 
ture readings  were  made  by  means  of  a  Pt-PtRd  thermo-couple, 
the  electromotive  force  of  which  was  determined  by  the  method 
of  balancing  against  a  standard  cell  by  means  of  a  potentiometer 
indicator. 

Owing  to  the  fact  that  by  mistake  water  was  used  in  making 
up  the  mixtures,  some  anhydrous  boric  acid  reverted  to  the 
hydrous  form.  This,  of  course,  made  it  troublesome  to  determine 
the  deformation  point  of  B2O3  owing  to  the  evolution  of  steam 
and  the  resulting  bubbling.  With  the  addition  of  o.i  SiOj, 
the  cones  seemed  to  stand  up  apparently  in  good  shape.  The 
heat  given  off  on  adding  water  to  the  6203.1.58102  mixture 
was  so  great  that  the  crucible  could  not  be  held  in  the  hand. 
At  the  same  time  very  little  heat  was  evolved  by  the  620.5.1.48102 
and  the  6203.1.68102  glasses.  On  fusing  the  6303.1.58102  mix- 
ture, it  assumed  a  pink  color. 

It  was  soon  observed  that  these  glasses  were  quite  viscous. 
This  was  illustrated  by  the  fact  that  a  twisted  platinum  wire  on 
being  lowered  into  the  fused  mass  and  again  raised  was  found  to 
draw  out  a  ribbon  of  glass.  It  is  not  surprising,  therefore,  that 
the  softening  points  could  not  be  checked,  in  spite  of  the  fact 
that  the  same  rate  of  heating  was  followed  as  closely  as  possible. 


A  THERMAL  STTDY  OF  IJOKIC  ACID-SIl.ICA  MIXTl'RUS.  5 


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6  A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 

In  going  over  this  part  of  the  work  four  times,  the  results  shown 
in  Fig.  I  were  obtained.  The  softening  points  of  the  mixtures 
beyond  BjOj.aSiOj  are  not  plotted  since  the  divergence  in  this 
part  of  the  series  is  still  greater. 

Softening  point  determinations  were  also  made  upon  rods 
drawn  from  all  of  the  fusions  but  these  likewise  gave  extremely 
variable  results,  considerably  lower  than  those  obtained  for  the 
cones. 

The  evidence  thus  far  collected  makes  it  apparent  that  any 
reaction  taking  place  under  these  conditions  would  be  greatly 
hindered  by  the  internal  molecular  friction. 

HEATING  AND  COOLING  CURVES. 
A  considerable  number  of  heating  and  cooling  curves  were 
determined  with  special  reference  to  the  6203.28100  mixture. 
The  latter  was  prepared  from  fused  B2O3  and  prepared  Si02,  and 
from  fused  boric  acid  and  flint,  passed  through  the  200  mesh 
sieve.  In  no  instance  was  there  a  temperature  acceleration  or 
lag  observed,  and,  hence,  the  observation  of  Binns  was  not  checked. 
In  Fig.  2,  the  heating  curve  in  which  the  couple  readings  were 
made  by  means  of  a  potentiometer  indicator  is  shown.  The 
junction  was  kept  at  0°  C.  by  means  of  ice.  In  Figs.  3  and  4, 
both  the  heating  and  cooling  curves  for  prepared  silica  and  flint 
mixtures  as  indicated  by  a  Siemens  and  Halske  recorder,  making 
a  contact  every  16  seconds,  are  presented.  It  was  observed 
that  on  fusing  an}'  mixture  of  B^Oj  and  SiO^,  imthout  previous 
fritting,  some  vapor  was  expelled  suddenly,  carrying  evidently 
a  certain  amount  of  boron.  This  happened  also  when  both  the 
boric  acid  and  silica  had  been  ignited  separately  to  constant 
weight  before  mixing.  Since  Professor  Binns  used  an  optical 
pyrometer,  it  is  quite  possible  that  by  focusing  upon  this  vapor 
the  readings  were  changed  as  observed  by  him. 

SOLUBILITY  DETERMINATIONS. 
The  diflerent  mixtures  were  fused  and  pulverized  on  cooling. 
The  resulting  powder  was  screened  through  the  80  and  150  mesh 
sieve.  All  material  coarser  than  the  80  and  finer  than  the  150 
mesh  was  rejected.  One  gram  samples  were  then  weighed  and 
put  in  stoppered  250  cc.  Erlenmeyer  flasks.     These  were  placed 


A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES.  7 


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A  THERMAL  STUDY  oF  IloKIC  ACIDSIl.ICA   MIXTl'RES.  9 

in  a  shaking  machine  together  with  200  cc.  of  distilled  water. 
After  shaking  for  10  hours  and  standing  over  night,  the  liquid 
was  filtered  olT  and  the  residue  washed.  Then  200  cc.  of  water 
was  again  added  (including  the  wash  water  used)  and  the  flasks 
were  again  shaken  for  one  hour.  The  residue  was  again  filtered 
and  washed.  After  drying,  the  residues  and  paper  were  ignited 
and  the  weights  determined.  The  insoluble  matter  in  each  case 
was  brushed  off  and  the  pajier  burnt  separately. 

The  weights  of  the  residues  are  shown  in  the  curve  of  Fig.  5. 


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It  is  seen  that  all  of  the  boric  acid  was  dissolved  in  the  first  of 
the  series  as  well  as  some  of  the  silica.  At  a  point  close  to 
B.,03.i.8SiO.,  however,  the  solubility  curve  crosses  the  line 
indicating  the  percentage  content  of  B/).,  (shown  by  the  dotted 
line)  which  proves  that  some  BjO^  has  been  rendered  insoluble. 
This  tendency  increases  with  the  silica  content.  At  the  molecular 
ratio  1:2a  decided  drop  occurs  indicating  the  rapid  formation  of 
an  insoluble  glass.  As  to  the  cause  of  this  sudden  change,  we 
can  only  conjecture  at  the  present  time.  To  establish  the  fact 
that  a  chemical  combination  has  taken  place  would  require  the 


lO  A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 

rimning  of  a  parallel  series  using  another  criterion  such  as  the 
specific  gravity  of  the  powder.  At  the  present  time,  however, 
this  evidence  might  be  used  to  support  the  claim  that  we  are 
dealing  here  with  a  solid  solution  representing  a  chemical  union 
between  the  silica  and  the  boric  acid. 

CONCLUSIONS. 

Fused  boric  acid-silica  mixtures  are  typical  glasses  pos- 
sessing no  definite  deformation  temperatures. 

No  thermal  phenomena  were  observed,  i.  e.,  there  was  no 
absorption  or  liberation  of  heat  throughout  the  series  B^Og  to 
BA-3SiO,. 

Boric  acid  when  fused  with  silica  first  dissolves  some  of 
the  latter.  The  amotmt  of  matter  solulple  in  water  decreases 
somewhat  more  rapidly  than  the  B^Og  content.  Between  2  and 
2.2  SiO,  a  decided  drop  in  the  solubility  of  the  glasses  occurs, 
indicating  that  some  B2O3  has  been  rendered  insoluble.  It  is 
quite  probable,  although  not  proven,  that  a  chemical  combina- 
tion might  take  place  at  this  point.  The  gradual  decrease  in 
solubility  might  thus  be  ascribed  to  the  formation  of  some  of 
this  combination  at  an  earlier  stage.  At  the  point  mentioned, 
a  more  rapid  enrichment  would  thus  take  place. 

DISCUSSION. 

Professor  Binns:  I  am  interested  in  the  results  secured  by 
Professor  Bleininger.  When  I  made  the  first  experiments  of 
this  kind  I  expressly  disclaimed  any  pretension  to  the  ability 
called  for  by  such  work,  and  I  based  my  chief  claim  as  to  the 
action  of  boron  upon  the  practical  issues  as  expressed  in  glaze 
composition.  From  this  position,  which  has  been  confirmed 
by  Dr.  Singer  and  ^Ir.  Stull,  I  have  not  had  cause  to  retreat. 


[Reprintkd  from  Transactions  American  Cbramic  Societv,     \\)L.  XIV. 

nv   Pkrmission  ] 

THE  REPLACEMENT  OF  TIN  OXIDE  BY  ANTIMONY  OXIDE 
IN  ENAMELS  FOR  CAST  IRON.' 

By  R.  E.  Brown,  Mt.  Savage,  Md. 

INTRODUCTION. 

Classification  of  Opacifiers. — Opacifiers  for  the  purposes  of 
this  work  are  divided  into  two  classes:  (i)  partial  opacifiers, 
and  (2)  absolute  opacifiers. 

In  the  first  class  are  included  bone  ash,  fluorite,  cryolite, 
and  silica.  Bone  ash  is  rarely  employed  in  enamels,  but  the  re- 
maining three,  especially  the  silica,  are  invariably  used.  Fluorite 
and  cr^'olite  are  advantageous,  commercially,  both  from  the 
standpoint  of  their  low  fusibility  and  their  fluorine  content. 
The  latter  gives  them  the  property  of  acting  as  weak  opacifiers, 
thereby  decreasing  the  amount  of  absolute  opacifier  needed.^ 
The  silica,  as  is  showTi  by  the  following  work,  has  no  opacifying 
tendencies  in  itself  in  this  type  of  glasses  but  emphasizes  and  in- 
creases the  opacity  brought  about  by  certain  opacifiers  proper. 

In  the  second  class,  the  opacifiers,  per  sc,  are  arsenious  oxide, 
zirconium  oxide,  tin  oxide  and  antimony  oxide.  Arsenious 
oxide  finds  a  very  limited  use,  being  employed  only  for  decorative 
work  on  jewelry  and  art  ware.  Zirconium  oxide  is  not  widely 
used;  while  some  consider  it  too  expensive  for  commercial 
work,  others  regard  it  a  cheap  opacifier  as  a  substitute  for  tin 
oxide. ^  Tin  oxide  is  by  far  the  most  widely  used  of  the  opacifiers, 
and  is  employed  not  only  in  the  enameling  of  sheet  iron  and  cast 
iron,  but  in  the  enameling  of  clay  products  as  well. 

Antimony  oxide  has  had,  to  date,  only  an  extremely  limited 
use  as  an  opacifier.  It  has  been  used  to  some  extent  in  Ger- 
many in  conjunction  with  zinc  oxide  as  a  substitute  for  tin  oxide.* 
It  has  been  used  in  this  country  to  some  extent,  and  in  one  case 
its  use  in  conjunction  with  other  ingredients  is  patented  as  "a 
substitute  for   tin   oxide. "^     In   a    "Note   on    White   Antimony 


'  Abstract  of  a  thesis  fulfiUins  part  of  the  requirements  for  the  detrree  of  Hachelor  of 
Science  in  Ceramics,  University  of  Illinois. 

-  .Mayer  and  Havas.  Sprechsaal,  XLII.  460-461. 

3  La  Ceramique.  11,   100-101.      Keram  Rundschau,  XVI.  89-91.   135-139. 

*  Ph.  Eyer,  Stahl  und  Eisen.  XVIII,  1097.  1099. 

5  U.  S.  Patent,  932,839. 


12      REPLACEMENT    OF  TIN    OXIDE    IN   ENAMELS   FOR    CAST    IRON. 

Enamels,"  Bock  points  out  the  dangers  of  the  use  of  antimony 
oxide  in  enamels  for  cooking  vessels,  but  no  mention  is  made  of 
its  employment  in  enamels  for  cast  iron." 

The  most  expensive  constituent  of  the  ordinary  commercial 
enamel  is  the  opacifying  agent,  tin  oxide,  both  by  reason  of  the 
high  market  price  and  the  quantity  employed.  The  prices  of 
antimony  oxide  and  tin  oxide  in  barrel  lots  are  at  present  10V2 
and  45  cents  per  pound,  respectively. 

Object  of  Work. — It  was  with  a  view  to  using  the  cheaper 
opacifier  for  cast  iron  enamels  that  this  work  was  undertaken. 
The  work  attempts  to  determine,  in  a  practical  way,  the  con- 
ditions under  which  antimony  oxide  may  be  used  in  enamels. 

EXECUTION  OF  WORK. 

Preparation  of  the  Enamels. — In  carrying  out  a  series  the 
ingredients  of  the  two  extremes  of  a  series  were  weighed  up  and 
mixed  thoroughly  by  passing  5  or  6  times  through  a  20  mesh 
screen.  The  batch  was  next  put  into  a  small  fare  clay  crucible 
(capacity  about  250  grams  of  the  raw  batch)  and  fritted  in  a  pot 
furnace,  fired  by  a  blast  lamp  using  artificial  gas  and  compressed 
air  as  fuel.  After  melting  and  becoming  relatively  free  from 
bubbles  the  contents  were  poured  into  water.  It  was  then  dried, 
again  put  into  the  crucibles  and  refritted,  care  being  taken  in 
this  second  fritting  to  prolong  the  heating  to  such  length  of  time 
that  no  bubbles  were  given  off.  As  soon  as  bubbles  had  ceased 
to  form,  the  contents  were  again  quenched  by  pouring  into  water. 
The  shattered  glass  was  dried  and  then  ground  in  8  inch,  porcelain, 
ball  mills  so  as  to  pass  a  200  mesh  sieve. 

The  two  extremes  of  a  series,  now  in  a  powdered  form, 
were  weighed  out  in  the  proper  proportions  to  form  the  inter- 
mediate enamels.  These  were  now  mixed  by  rubbing  5  or  6 
times  through  a  60  mesh  sieve. 

The  Ingredients. — ^The  raw  ingredients  employed  in  intro- 
ducing the  following  constituents  with  the  molecular  weights 
used  were  as  follows : 

ZnO:     Introduced  as  zinc  oxide  (81). 

PbO :     Brought  in  as  red  lead  Fhfi,  (685) . 


schem.  Ztg.,  XXXII,  516-517. 


REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR    CAST    IRON.      1 3 

BaO:  Where  employed,  was  brought  in  by  barium  car- 
bonate (197). 

CaO:  Brought  in  by  lluorite  (78),  whiting  (100),  and 
hydrated  lime  (74). 

Na.,0:  Introduced  as  sodium  carbonate  (io6),  borax  (382), 
and  cryolite  (210). 

K^O:  Brought  in  by  potassium  nitrate  (loi)  and  potash 
feldspar  (557). 

MgO:  Brought  in  by  magnesium  carbonate  (84)  and 
magnesium  oxide  (40). 

AI2O3:  Potash  spar  (557)  was  used  as  the  main  source  of 
alumina.  Small  amounts  of  cryolite,  NaaAlFg  (210)  were  also 
used. 

B2O3;  This  was  brought  in  by  using  borax  (3S2)  in  the  cover 
enamels  and  as  borax  and  boric  acid  (62)  in  the  ground  coats. 

SnO, :     Brought  in  as  tin  oxide  (150). 

Sb^Og:     Introduced  as  white  oxide  of  antimony  (288). 

SiOa:     Brought  in  as  potash  feldspar  (557),  and  as  flint  (60). 

In  addition  to  the  above  ingredients,  ammonium  carbonate 
was  used  in  some  of  the  enamels  of  the  later  series.  This 
volatilizes  readily  and  serves  as  a  clarifier  of  bubbles  in  the  glass 
during  fritting. 

Trial  Pieces. — The  trial  pieces  were  small  circular  discs 
Vs"  thick  and  2"  in  diameter  with  a  raised  center.  The  iron 
used  for  casting  these  trials  did  not  prove  to  be  of  a  very  satisfac- 
tory grade  as  it  frequently  produced  large  bubbles  or  blisters  in 
the  enamels,  probably  due  to  the  sulphur  content  of  the  iron. 

The  trials  were  cleaned  by  pickling  for  20-30  minutes  in  a 
dilute  solution  of  hydrochloric  acid  so  as  to  remove  the  scale 
and  any  oxide  present.  After  this  they  were  washed  and  scrubbed 
and  then  dipped  in  a  dilute  solution  of  sodium  carbonate  so  as  to 
neutralize  all  of  the  acid.  They  were  then  scrubbed  and  washed 
again,  the  surface  water  was  wiped  ofif,  and  the  trials  were  put. 
into  a  warm  oven.  Even  with  this  seemingly  thorough  treat- 
ment, the  coat  of  carbon  (left  by  dissolving  the  iron)  was  not; 
entirely  removed,  and  hence  gave  rise  to  bubbles  during  the  burn- 
ing process.  Another  method  of  cleaning  the  iron,  used  in  the 
latter  part  of  the  work,  proved  very  effective.     In  this,  the  iron 


14    REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    FOR    CAST    IRON. 

was  pickled  as  before  and  then  put  into  a  ball  mill  with  sand  and 
water;  thus  all  of  the  carbon  was  effectually  removed  with  the 
result  that  less  trouble  as  regards  bubbling  was  experienced. 

The  ground  coat  was  applied  to  the  trials  by  dipping,  care 
being  taken  to  secure  a  thin  coat  that  was  as  uniform  as  possible. 

Composition  of  the  Ground  Coat. — The  ground  coat  chosen 
was  of  the  composition  shown : 

0.30    K,0       ] 

0.24    Na,0      I0.297AUO3 

[-2.19  SiOa 
0.31  BA     j 


o.  159  CaO 
0.219  MgO 
0.081  PbO 


Batch  weights:  15  flint;  30  potash  feldspar;  10  boric  acid; 
5  KNO3;  5  PbgO,;  2.2  Ca(0H)2;  2.3  MgO;  lo.o  cryolite;  i.o 
fluorite. 

The  trial  piece,  after  being  slush  coated  and  dried,  was 
placed  in  the  furnace,  which  had  been  heated  to  the  temperature 
of  burning.  As  soon  as  the  iron  had  attained  a  sufficient  heat 
for  fusing  the  ground  enamel,  it  appears  to  "melt"  not  unlike 
^  coat  of  frost  or  snow.  This  commences  at  one  spot  and  soon 
lias  extended  over  the  whole  trial.  The  trial  now  has  a  glossy 
appearance.  Almost  coincident  with  this,  innumerable  bubbles 
are  formed  which  "break"  at  once.  This  continues  for  a  short 
time,  after  which  the  glossy  coating  or  glass  smooths  down. 
It  is  at  this  point,  in  the  writer's  judgment,  that  the  burning  of 
the  ground  coat  is  complete.  If  the  trial  is  not  removed  at  once, 
larger  bubbles  are  formed,  but  the  glass  is  then  decidedly  more 
viscous  than  when  the  preliminary  bubbles  were  formed.  When 
they  break,  if  they  break  at  all,  they  leave  a  rough  slag  on  the 
surface  of  the  trial  as  is  shown  by  cooling  the  trial  piece. 

Burning  the  Enamels. — ^The  furnace  used  for  the  enameling 
was  of  the  open-fired  type,  i.  e.,  without  a  muffle  chamber,  and 
was  fired  by  the  use  of  artificial  gas  and  compressed  air  as  fuel. 
Although  this  is  not  the  type  of  furnace  best  suited  for  this  kind 
of  work,  it  was  the  only  one  available  and  there  was  no  time  for 
the  construction  of  a  more  suitable  one.  The  temperature  of 
burning  was  measured  by  a  Le  Chatelier  pyrometer,  the  couple 
of  which  was  inserted  so  that  its  junction  point  was  at  the  side 


REPLACEMEXT    OF   TIN    OXIDE    IN    ENAMELS    FoR    CAST    IRON.      15 


of  the  trial.  The  holder  for  the  trial  piece  consisted  of  a  bar  of 
iron  "upset"  at  one  end  and  so  shaped  as  to  fit  on  the  inside  of 
the  trial  piece. 

Series  I. 

REPLACEMENT     OF     TIN    OXIDE      HV     ANTIMONY     OXIDE    IN    A    TIN 

ENAMEL. 

This  series  was  carried  out  by  replacing  the  tin  oxide  in  an 
enamel  similar  to  that  given  by  Riddle  in  his  "Types  of  Enamels 
for  Enameling  Cast  Iron  Sanitary  Ware,"  Trans.  A.  C.  S.,  Vol. 
IX,  with  antimony  oxide,  thus: 

0.25  Na^O   1 

o.  10  MgO     I 

0.15  PbO      jo.isAIAl    i.ooSiO. 

0.15  BaO  i 

0.15  KjO        0.20  B2O3  J  o.  15  SnO^-o.oys  Sb^Oj 

0.05  ZnO 

0.15  CaO 

Batch  formulae  (in  equivalents). 


cti 


n 


o 


N 


PQ 


Ui 


VI 


tfl 


2 

3 
4 
5 


0.15 
0.15 
0.15 
0.15 
0.15 


0.05 
0.05 
0.05 
0.05 
0.05 


0.15 
0.15 
0.15 


0.15 
0.15 
0.15 


0.150. 15 
o. 150.15 


0.05 
0.05 
0.05 
0.05 
0.05 


O.IO 

o.  10 
o.  10 
o.  10 
o.  10 


o.  10 
o.  10 
o.  10 
o.  10 
o.  10 


0.15 
0.15 

0.15 
0.15 
0.15 


o.  10 
o.  10 
o.  10 
o.  10 
o.  10 


0.15 
O.II25 
0.075 
0.0375 

0.00 


0.00 

0.0188 

0.0375 

0.056 

0.075 


Description  of  Trials. — No.  i  is  a  good  enamel  and  is  a 
typical  tin  enamel.  All  of  the  rest  of  the  series,  with  the  possible 
exception  of  No.  2,  are  very  poor.  A  peculiar  "puckery"  or 
matte  texture  exists,  the  surface  is  rough  and  uneven,  and  the 
enamel  flies  off  in  patches,  resembling  shivering  of  clay  ware. 
In  the  trials  of  enamels  3  and  4,  the  "puckery"  effect  is  partially 
overcome  by  laising  the  burning  temperature.  The  shivering 
is  also  lessened  by  this  treatment.  It  is  also  evident  in  this 
series  as  well  as  in  the  rest  of  the  work  that  where  an  enamel  is 
applied,  too  thick  shivering  is  more  likely  to  occur. 

Thinking  perhaps  that  the  "puckery"  effect  might  be  over- 
come partially  by  making  a  more  easily  fusible  enamel  it  was 


1 6    REPLACEMENT   OF   TIN    OXIDE    IN   ENAMELS   FOR    CAST    IRON. 


decided  to  run  a  series  with  a  more  fusible  RO  combination. 
It  was  also  suggested  that  the  "puckery"  effect  might  be  due 
to  the  barium  which  reacted  with  the  sulphur  present  in  the 
SbjOg.^  Some  of  the  Sb203  was  tested  and  found  to  contain 
sulphur. 

A  series  embodying  the  two  above  ideas  was  accordingly 
carried  out  as  given  below.  Although  it  was  not  conducted 
strictly  on  a  scientific  basis  it  is  sufficient  to  show  in  a  practical 
way  the  desired  effect. 

Series  II. 

VARIATION     OF     BARIUM    OXIDE     AND     ITS    EFFECT    ON     ANTIMONY 

OXIDE. 
0.25-0.54  NaoO 
o.  lo-o.oo  MgO 

o.  15-0'.  15  PbO        o.  15-0. 16  AI2O3  ]   i.ooSiOj 
o .  1 5-0 . 1 6  KjO      }  } 

0.05-0.05  ZnO      I  0.20  B2O3  J  0.075  SbjOg 

o.  15-0. 10  CaO      1 
0.15-0.00  BaO     J 


Batch  formulae  (in  equivalents). 


d 

0      "S 

0 
0 

fa 

SI 

0 

0 

d 
N 

0 

•z 

4) 

"o 

>> 

u 
U 

0 

0 

i 

0 
0 

BO 

% 

1^ 

a 

S 

w 

I 

2 

3 

4 

0.15 
0.21 
0.29 

0-35 

0.05 
0.05 
0.05 
0.05 

0.15 
0. 10 
0.05 
0.00 

0.15 

0. 10 

0.05 
0.00 

0.05 
0.05 
0.05 
0.05 

0.00 
0.02 
0.04 
0.06 

0.00 
0.02 
0.04 
0.06 

0.00 
0.03 
0.07 
0.  10 

O.IO 

0. 10 
0. 10 

O.IO 

O.IO 

0.07 

0.03 
0.00 

0.15 
0.148 
0.136 
0.13 

0.  10 
0.  14 
0.18 
0.22 

0.075 
0.075 
0.075 
0.075 

Description  of  Trials. — The  "puckery"  effect  has  decreased 
toward  the  end  of  the  series  which  contains  no  barium  and  in 
No.  4  is  not  present  at  all.  This  enamel  is  a  fair  enamel  which 
adheres  well.  No.  i  is  somewhat  shivered.  This  series  shows 
from  a  practical  standpoint  that  barium  should  not  be  used  to 
any  very  large  extent  in  an  enamel  where  there  is  a  contact  with 
sulphur  gases.  Its  use,  however,  in  enamels  where  tin  is  used  as 
an  opacifier  is  very  much  desired,  owing  to  its  ability  to  decrease 
shivering. 


''  Sb203  is  prepared  from  stibnite,  Sb2S3,  by  roasting  in  air,  hence  sulphates  are  formed 
which,  if  not  entirely  removed,  would  combine  with  the  barium  compounds. 


REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    FOR    CAST    IRON.    1 7 


Series  III. 

VARIATION   OF  THE   SILICA   CONTENT. 
This  series  was  varied  between  the  limits  of  i.oo  and  2.00 
•equivalents  of  silica  as  shown : 


o.ioCaO 
o .  54  NaoO 
0.15  Pbb 
0.16  K,0 
0.05  ZnO 


0.16  Al A 

0.20     B,Oq 


1 .00-2  .00  SiOj 
0.075  vSboOj 


Batch  formulae  (in 

squivalents). 

6 

2: 

0 

a 
Z 

1   '  i 

0 

V 

>• 

Wi 

0 

0 

0 

i 

a 

c 
S 

0 
1 

I 

2 

3 

4 

5 

6 

7 

8 

9 

0.35 
0.35 
0.35 
0.35 
0.35 
0.35 
0-35 
0.35 
0.35 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.05 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.06 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.  ID 

0.  10 
0.  10 
0.  10 
0.  10 
0.  10 
0.  10 
0.  10 
0.  10 

O.IO 

0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 

0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 

0.22 

0.345 
0.47 

0.595 
0.72 
0.845 
0.97 
I  095 
1 .22 

0.075 
0.075 
0.075 
0.075 
0.075 
0.075 
0.075 
0.075 
0.075 

Description  of  Trials. — Nos.  i,  2  and  3  have  an  egg  shell- 
like texture  but  otherwise  are  fair  enamels.  The  trials  of  enamels 
Nos.  4  and  5  are  better  and  do  not  show  the  above  texture  to  such 
a  degree.  No.  6  is  a  fair  enamel  but  is  a  trifle  dull.  No.  7  is  a 
good  enamel  and  adheres  well.  It  is  whiter  and  has  a  better 
gloss  than  the  average  commercial  enamel.  Enamel  No.  8  is 
whiter  than  No.  7  and  has  a  better  gloss.  A  few  of  the  trials 
shiver  somewhat,  showing  that  the  silica  is  a  trifle  too  high. 
Enamel  No.  9  has  shivered  still  more,  but  on  the  trials  where 
it  held,  it  is  the  whitest  and  most  brilliant  of  the  series.  Enamels 
Nos.  8  and  9  have  an  exceptionally  white  color  and  are  more  than 
the  equal  of  the  average  tin  enamel  in  this  respect. 

The  result  of  this  series  seems  to  show  that  the  last  two 
enamels  are  too  high  in  silica  and  also  that  a  silica  content  of 
over  1.85  equivalents  is  conducive  in  shivering.  The  burning 
temperature  rises  as  the  silica  content  increases;  but  this  heat, 


1 8   REPLACEMENT   OF   TIN    OXIDE    IN   ENAMELS   FOR   CAST   IRON. 


even  with  the  enamels  containing  2.0  SiOj,  did  not  cause  the  iron 
to  deteriorate  to  any  visible  extent.  As  silica  increases,  the 
whiteness  is  increased,  and  it  is  evident  that  a  sacrifice  must  be 
made  of  part  of  the  whiteness  in  order  to  obtain  enamels  that 
do  not  shiver. 

Series  IV. 

VARIATION    OF    ALUMINA. 

This  series  was  run  between  the  limits  of  o.i  and  0.2  equiv- 
alent of  AI2O3.  To  bring  in  the  AUOg  in  combined  form,  i.  e., 
as  spar,  it  was  necessary  to  change  the  RO  with  respect  to  K2O 
and  NajO  thus: 


o.  16-0.20  K^O 

0.15  PbO 

o. 10  CaO 

o .  54-0 .  50  Na20 

0.05  ZnO 


o.  10-0.20  ALO,  1   1.80  SiO, 


o .  20  B,0, 


0.075  SbPa 


Batch  formulae  (in  equi 

valents). 

6 

0 

•a 

0 

a 
N 

0 

0 
IZ 

V 

0 

g 

0 

1 

I.  .  .  . 

3.... 

4 

5.  ... 
6 

0.35 
0.342 

0-334 
0.326 
0.318 
0.31 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.06 

0.049 

0.038 

0.025 

0.013 

0.00 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

O.IO 
O.IO 

0.16 

O.IO 
O.IO 
O.IO 

O.IO 
O.IO 
O.IO 
O.IO 
O.IO 
O.IO 

0.07 
0.09 

O.I  I 

0.13 
0.15 
0.17 

1.38 
1.26 
1. 14 

1.02 
0.90 

0.78 

0.075 
0.075 
0.075 
0.075 
0.075 
0.075 

Description  of  Trials. — All  enamels  of  the  series  are  good 
enamels  with  whiteness  increasing  toward  No.  6,  i.  e.,  with  in- 
crease of  AI2O3.  The  temperature  required  for  maturing  increases, 
however,  with  the  AI2O3.  The  best  enamel  of  the  series,  taking 
burning  temperature,  whiteness,  gloss,  and  adhesive  properties 
into  consideration,  is  No.  4  containing  0.16  AI2O3. 

Series  V. 

VARIATION    OF    ANTIMONY    OXIDE. 

This  series  as  well  as  the  remaining  two  series  was  carried 
out  in  two  parts,  A  and  B,  the  two  parts  being  practically  alike 


REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR    CAST    IRON.    I9 

-except  for  the  silica  content.  Part  B  was  carried  out  first  and  the 
limits  of  Sb.O.,  were  not  high  enough,  hence  these  were  changed 
in  A. 

Series  V,  A. 

0.16  K.O     1 

0.05  ZnO        0.16  AUO3  1   1 .8  SiO. 

o.ioCaO      I  I- 

o.isPbO     |o.2oB,03    Jo-o.i4Sb203 

o .  54  NajO  J 


0.16K2O 
0.05  ZnO 
o.  10  CaO 
0.15  PbO 
0.54  NajO 


Series  V,  B. 

0.16  A1,0,       2.0  SiO,. 

"     \ 
o .  20  B2O3     J  0-0 . 1 1  SbjO, 


V,  A.     Batch  formulae  (in  equivalents). 


c 
a: 

■0 

0.35 

0.05 

0-35 

0.05 

0.35 

0.05 

0.35 

0.05 

0.35 

0.05 

0.35 

0.05 

0.35 

0.05 

0.35 

0.05 

N 


O 


a 

O 


CQ 


'U, 


I . 

2  . 

3- 
4- 
5- 
6. 

7 


0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 


0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 


0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 


o.  10 
o.  10 
o.  10 
o.  10 
o.  10 
o.  10 
o.  10 
o.  10 


o.  10 
o.  10 
o.  10 
o.  10 
o.  10 
o.  10 
o.  10 
o.  10 


0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 


1 .02 
1 .02 
1 .02 
1 .02 
1 .02 
1 .02 
1 .02 
1 .02 


0.00 
0.02 
0.04 
0.06 
0.08 

o.  10 

O.  12 

0.14 


V,  B 

Batch  formulae  (in  equi 

valents 

)■ 

d 

•z 

0 

«    1    ,5 

c        1          c         2 

u 

■x. 

s        £ 

I 

3 

4 

5 

6 

0.35 

0-35 
0.35 
0.35 
0.35 
0.35 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.  10 
0.  10 
0.  10 
0.  10 
0.  10 
0.  10 

O.IO 
O.IO 

0. 10 
0. 10 
0. 10 
0. 10 

0.13 
0.13 
0.13 
0.13 
0.13 
0.13 

I  .22 
I  .22 
I  .22 
I  .22 
I  .22 
I  .22 

0.00 

0.022 

0.044 

0.066 

0.088 

0.  II 

Description  of  Trials. — The  trials  of  enamel   i  A  have  but 


20      REPLACEMENT    OF    TIN    OXIDE    IN    ENAMELS   FOR    CAST    IRON. 

slight  opacity.  Xo.  2  A  has  a  trifle  more  and  so  on  up  the  series, 
Enamel  Xo.  3  A  has  a  fair  opacity,  Xo.  4  A  and  5  A  are  good 
enamels,  Xo.  5  A  being  the  whitest.  Xo.  6  A  is  a  good  enamel. 
It  is  whiter  than  Xo.  5  but  is  not  quite  so  glossy.  Xo.  7  is  a  good 
enamel  and  is  a  trifle  "matte"  in  texture.  Xo.  S  has  a  beautiful 
matte  texture  and  differs  from  all  the  rest  of  the  series  in  this 
respect.  One  of  the  trials,  however,  shows  a  tendency  to  shiver 
but  this  may  possibly  be  due  to  the  mode  of  application.  Enamel 
Xo.  5  is  the  best  of  the  A  part  of  the  series,  taking  gloss,  finish, 
and  general  appearance  into  consideration,  while  for  a  dull  or 
matte  texture  Xo.  S  is  the  best.  Enamels  Xo.  7  and  8  require 
a  higher  temperature  for  burning,  thus  indicating  that  high 
antimony  decreases  the  fusibility. 

With  part  B  of  the  series  shivering  is  more  evident  in  every 
case.  The  enamels  which  held  are,  however,  of  greater  brilliancy 
and  opacity,  enamel  Xo.  2  of  A  being  identical  in  appearance 
with  Xo.  I  of  B.  Enamels  2,  3  and  4  of  part  B  are  practically 
the  same  as  3,  4  and  5  of  part  A  respectively.  From  this  we  would 
conclude  that  0.016  equivalent  of  Sb,03.  in  this  range  of  silica 
content,  has  about  the  same  opacifying  effect  as  0.02  equivalent 
of  silica. 

Series  VI. 

REPLACEMENT  OF  ANTIMONY  OXIDE  BY  TIN  OXIDE  IN  AN  ANTIMONY 

ENAMEL. 

This  series,  also  using  two  different  equivalents  of  silica., 
was  carried  out  as  follows : 

VI,  A. 
o.i6K,,0 

0.05  ZnO      1  o.  16  AUO3    '    1 .80  SiO. 
o .  10  CaO      [•  } 

0.15  PbO     I  0.20  B2O3     J  0.075  Sb203-o.i5  SnO, 
o .  54  Na^O   J 


VI,  B. 
0.16  K,0     1 

0.05  ZnO      I  o.  16  AUO3    ~   2.0  SiO., 
o .  10  CaO      >  > 

0.15  PbO     I  0.20  B2O3     J  0.075  Sb203-o.i5  SnO, 
0.54  Xa.P   J 


REPLACEMENT    ( )F   TLN    OXIDE    L\    ENAMELS    FOR    CAST    IRON.      2  1 


Batch  forimilae  (in  equivalents). 
VI.  A. 


6 
2: 

§ 

d 
2 

R.  Lead 

C 

s 

C 
12 

>• 

0 

0 

n 
u 

0 

ca 

u 
X 

b 

c 

i 

0 

c 

I.  . . . 

0.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.02 

0.075 

0.00 

0.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.10 

0.13 

1.02 

0.056 

0.038 

3 

0.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.02 

0.038 

0.075 

4 

035 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.02 

0.019 

0.II25 

5 

0-35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.02 

0.00 

0.15 

VI,  B. 


I.  . . . 

0.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.075 

0.00 

2.  .  .  . 

0-35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.056 

0.038 

3.... 

0-35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.038 

0.075 

4 

0.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.019 

O.II25 

5.  ... 

0.35 

0.05 

0.05 

0.0^ 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.00 

0.15 

Description  of  Trials. — All  enamels  of  the  A  part  of  the  series 
adhere  tenaciously  and  are  good  enamels.  Enamel  No.  i  has 
more  opacity  and  whiteness  than  No.  5,  these  two  properties 
decreasing  uniformly  between  these  extremes.  The  antimony 
enamel  requires  a  slightly  higher  temperature  for  maturing,  but 
not  to  such  extent  as  to  be  detrimental  to  the  iron. 

In  the  B  part  of  the  series  shivering  is  much  in  evidence, 
due  to  the  increased  silica.  Enamels  Nos.  i  and  2  have  good 
opacity  but  Nos.  3  and  4  are  much  inferior  in  this  respect.  In 
enamel  No.  5  the  silica  has  dissolved  the  SnOj  almost  entirely. 
Taking  the  results  of  this  series  we  would  conclude  that  SiO, 
at  the  higher  limit  is  opposite  in  effect  with  regard  to  SboOg  and 
SnO,.  In  the  case  of  Sb203  the  opacity,  whiteness  and  brilliancy 
are  increased,  while  with  vSnO,  these  properties,  notably  the 
opacity,  are  decreased.  Shivering,  however,  is  increased  in 
either  case.  The  results  obtained  in  part  A  of  the  series  are  not 
in  accord  with  those  of  Riddle  whose  high  limit  of  silica  was  1.23 
equivalents.  In  enamel  No.  5  part  A  as  given  above,  a  good 
white  enamel  was  obtained  using  1.8  equivalents  of  silica. 

It  might  be  interesting  to  note  also  at  this  point,  the  be- 
havior of  the  enamels  on  wTought  iron.  The  enamels  of  part 
A  were  applied  to  iron  washers,  and  although  they  had  not  been 


22      REPLACEMENT   OF   TIN    OXIDE    IN   ENAMELS    FOR    CAST    IRON. 

previously  cleaned,  the  enamels  held  perfectly  and  were  of  good 
whiteness,  brilliancy  and  texture. 

Series  VII. 

VARIATION    OF    BORIC    OXIDE. 

This  series  employs  two  equivalents  of  silica  and  the  NajCOg 
content  is  varied  in  order  to  reach  the  lower  limit  of  B2O3  still 
maintaining  the  same  ratio. 


0.16  KoO 
0.05  ZnO 
o.  10  CaO 
0.15  PbO 
0.54  NaoO 


VII,  A. 
0.16  AI2O3  1    1.80  SiOa 

0.10-0.40  B2O3  J  0.075  Sb203 

VII,  B. 

1  2.00  SiO, 


0.16K2O     1 

0.05  ZnO      I  o.  16  AI2O3 

o.  10  CaO      } 

0.15  PbO     I  0.10-0.40  B2O3   J  0.075  Sb203 

0.54  Nap   J 

VII,  A. 
Batch  formulae  (in  equivalents) 


1 

0 
0 

(S 

•d 
>A 
pi 

0 

a 

0 

Cryolite 
Ca(OH)2 

Borax 
K.  Spar 

0 

I 

0.4 

0-375 

0.350 

0.325 

0.300 

0.275 

0.25 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.03 
0.03 
0.03 
0.03 
0.03 
0.03 
0.03 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

O.IO 
O.IO 
O.IO 
O.IO 
O.IO 
O.IO 
O.IO 

0.05 

0.075 

O.IO 

0.125 
0.150 
0.175 

0.2 

0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 

1.02 
1.02 
1.02 
1.02 
1.02 
1. 02 
1.02 

0.075 
0.075 

3 

4 

5 

6 

7 

0.075 
0.075 
0.075 
0.075 
0.075 

VII,  B. 


0.4 

0.05 

0.05 

0.03. 

0.06 

O.IO 

0.05 

0.13 

1.22 

0.075 

0.375 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.075 

0.13 

1.22 

0.075 

0-350 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.075 

0.325 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.125 

0.13 

1.22 

0.075 

0.300 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.150 

0.13 

1.22 

0.075 

0.275 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.175 

0.13 

1.22 

0.075 

0.250 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.200 

0.13 

1.22 

0.075 

REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    FOR    CAST    IRON.      23 

Description  of  Trials. — All  enamels  of  part  A  adhere  well 
and  are  good  white  enamels  up  to  No.  6.  Nos.  6  and  7  liave  a 
yellowish  cast  and  are  not  all  desirable  enamels.  Bubbling  is 
also  evident  in  the  enamels  of  higher  BJJ.^  content.  Enamel  No. 
I  is  the  whitest  of  the  five  enamels. 

The  results  obtained  in  part  B  are  substantially  the  same  as 
those  of  part  A.  The  enamels  are  whiter,  however,  than  the  ones 
of  the  same  B/).,  content  and  the  yellowish  cast  of  enamels  6 
and  7  of  part  A  has  disappeared  in  the  corresponding  enamels  of 
part  B.  Shivering  is  present  to  quite  a  large  extent  in  part  B, 
due  to  the  high  silica.  As  in  part  A,  bubbling  is  prominent 
in  the  enamels  of  the  higher  B.Oj  content.  The  dilTerence  in 
whiteness  of  the  high  and  low  B.O^  enamels  in  part  A  is  not  so 
pronounced  in  this  part  of  the  series.  Enamels  B  i  and  B  7 
have  very  little  difference  in  whiteness,  B  i  being  a  little  the 
whitest.  The  difference  in  maturing  temperature  is  however 
quite  large  and  the  tendency  to  bubbling  is  more  evident. 

The  results  indicate  that  the  lower  the  B^O^  the  better  and 
whiter  are  the  enamels.  The  limits  for  desirable  enamels  are 
about  0.15-0.30  B2O3. 

LIMITS  OF  THE  INGREDIENTS. 

The  limits  of  the  ingredients  and  their  effects  established 
by  this  work  are  as  follows : 

SiO^:  The  effect  of  silica  is  to  increase  brilliancy,  white- 
ness, acid-resisting  properties  and  gloss.  If  increased  too  high, 
shivering  takes  place  and  the  maturing  temperature  is  too  high. 
The  limits  are  about  i. 65-1. 85  equivalents,  those  nearer  the 
higher  limit  being  the  preferable. 

Al.,0.j :  Increased  AljO.,  increases  the  temperature  for  matur- 
ing and  gives  whiter  enamels.  The  high  limit  is  around  0.18 
equivalent.  The  low  limit  was  not  established  but  for  com- 
mercial enamels  is  probably  about  0.13  equivalent. 

Sb^O^:  The  effect  of  vSb._,0.j  is  to  increase  the  maturing  tem- 
perature, and  to  increase  the  whiteness  and  opacity  when  em- 
ployed between  the  limits  of  0.0-0.09  equivalent  Sbp^.  If 
used  between  the  limits  of  0.1-0.14  equivalent  the  enamels  are 
dull  at  the  lower  limits  and  matteness  increases  at  the  higher. 


24     REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR    CAST    IRON. 

At  the  high  Hmit,  0.14  equivalent,  shivering  is  Hkely   to   occur. 

For  brilliant  enamels  of  good  opacity  and  texture  the  limits 
are  0.06-0.09  equivalent,  about  0.075  being  preferable. 

vSnO.:  No  variation  of  the  SnO.  content  was  made  but  a 
good  enamel  was  obtained  using  0.15  equivalent  of  SnO,. 

B,0., :  The  effect  of  increased  B.Og  is  to  lower  the  maturing 
temperature,  to  increase  the  tendency  to  produce  bubbles,  to 
decrease  the  whiteness  when  used  above  a  certain  limit,  increase 
o-loss  and  to  increase  the  solubility  of  the  enamel.  The  limits 
are  about  0.15-0.3  equivalent,  those  nearer  the  lower  limit  being 
preferable. 

BaO:  The  effect  of  BaO  in  Sb.O.,  enamels  is  to  produce  a 
"puckery"  or  matte  effect.  This  is  no  doubt  due  to  the  sulphur 
arising  from  the  Sbp.;  and  the  fuel  gases,  which  comes  in  contact 
with  the  barium  compounds. 

The  most  likely  enamel  taking  all  points  into  consideration 

is: 

o.i6K,0    1 

0.05  ZnO        o.i6Al,,0,    I   i-SoSiO, 


o.  10  CaO 

0.15  PbO      I  0.20  B2O3     J  0.075  SbPa 

0.54  Na,0   J 

•  DISCUSSION. 

Professor  Staler:  Why  do  you  not  include  the  fluorine  in 
your  formula?  No  one  will  be  able  to  calculate  the  batch  from 
the  formula  unless  you  do  so.  Moreover,  it  makes  a  vast  differ- 
ence whether  an  enamel  contains  a  small  or  a  large  amount  of 
this  element. 

Mr.  Brown:  I  do  not  think  it  is  necessary.  I  introduced 
it  as  cryolite,  using  0.06  equivalent  of  cryolite  throughout. 

Professor  Sialcy:  Mr.  Brown,  I  just  want  to  ask  one  more 
question.  Did  you  get  an  absolutely  pure  white  enamel,  or  was 
it  of  a  greenish  or  bluish  tint?  There  have  been  many  attempts 
made  to  use  antimony  in  place  of  tin  oxide  in  cast  iron  enamels, 
but  it  has  never  given  a  satisfactory  white.  They  get  a  tint 
they  call  white,  but  it  is  not  a  commercial  white.  Do  you  have 
any  idea  of  how  to  avoid  getting  that  greenish,  bluish  white  so 
characteristic  of  antimony  oxide? 


REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    KOR    CAST    IRON.      25 

Mr.  Broiin:  I  did  not  carry  on  work  to  eliminate  the  cast 
you  speak  of.  The  cast  was  not  present  to  an  a^^sravated  extent 
that  I  could  see.  A  number  of  others  said  the  same  thing.  Tliere 
is  a  slight  bluish  cast  or  tint  in  some  of  the  trials. 

Professor  Staler:  In  your  ilnal  enamel  as  well  as  in  all  the 
others  ? 

Mr.  Brown:  It  was  not  so  pronounced  in  this  case,  but 
more  so  in  the  enamels  of  higher  silica  content. 

Mr.  Burt:  I  noticed  in  speaking  of  the  enameled  iron 
industry  they  always  speak  of  dusting  the  enamel  on  and  I  would 
like  to  get  a  little  description  of  what  the  mechanical  process  is — 
of  what  is  involved  in  this  dusting  on  of  the  glaze. 

Professor  Staley:  In  a  paper  ("  The  Manufacture  of  Enameled 
Iron  Sanitary  Ware,"  Trans.  A.  C.  S.,  \'ol.  V'lII,  p.  172)  I  pub- 
lished several  years  ago,  you  can  find  a  description  of  the  ordinary 
method  of  making  a  piece  of  enameled  cast  iron.  The  only 
difference  between  the  method  described  there  and  the  method 
used  at  present  is  the  use  of  a  mechanical  agitator. 

Mr.  Burt:     What  mesh  sieve  do  you  use? 

Professor  Staley:     The  sieve  is  a  fifty-  or  sixty-mesh  sieve. 

Mr.  Brown:  I  would  like  to  ask  Professor  Staley  what  his 
opinion  is  of  the  lluorine  in  a  fused  enamel — ^whether  it  is 
volatilized  or  whether  it  is  retained  in  the  enamel.  I  have  read 
of  several  instances  where  they  analyzed  for  lluorine  and  found 
it  in  the  enamels  in  small  quantities. 

Professor  Staley:  That  is  all  a  matter,  in  my  mind,  of  how- 
hard,  how  long,  and  how  hot  you  heat  the  enamel.  You  can 
volatilize  it  all,  ot  you  can  have  the  larger  portion  of  it  stay  in. 
If  it  is  all  volatilized  you  have  no  opacifying  effect  from  the  use  of 
fluorides.  In  cast  iron  enamels  that  are  heated  or  fritted  in  the 
ordinary  length  of  time,  the  large  bulk  of  fluorine  stays  in. 

NOTE  PREPARED  AFTER  READING  THE  PAPER. 

Professor  Bleininger:  It  seems  to  me  that  Mr.  Brown  has 
solved  his  problem  satisfactorily.  He  has  accomplished  two 
things,  viz.,  the  production  of  a  white  enamel  wliicli  compares 
favorably  with  the  best  tin  enamels,  in  the  opinion  of  impartial 
observers,  and  he  likewise  has  shown  clearly  the  kind  of  enamel 


26     REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR   CAST    IRON. 

required  for  the  use  of  antimony  as  an  opacifier,  which  differs 
somewhat  from  the  common  t^^pe. 

As  regards  the  poisonous  quaUty  of  antimony  compounds. 
Rickmann,  Sprechsaal,  XL^^  115-117,  says  that  during  an  ex- 
perience of  ten  years  the  use  of  metasodium  antimonate  has  not 
proven  injurious.  However,  he  points  out  that  the  antimony 
oxide  compounds  (tartar  emetic,  etc.)  are  poisonous.  For  cast 
iron  enamels,  therefore,  the  use  of  Na^Sb^Oa  might  be  a  perfectly 
feasible  solution. 


